Figure



Jan. 21, 1964 o. G. FULFORD ,3 6

SPROCKE'I WHEELS Filed Jan. 2, 1962 2 Sheets-Sheet 1 I I 26 l INVENTOR05622 7 63 Fzdford ATTORNEYS Jan. 21, 1964 o. G. FULFORD SPROCKET WHEELS2 Sheets-Sheet 2 Filed Jan. 2, 1962 INVENTOR Wiper G. FzaZf'ord ii/mammm ATTOR NEYS United States Patent T 3,118,316 SPROCKET WEEELS Oliver G.Fulton-d, 917 Fuiiord Road, ()cala, Fla. Filed Jan. 2., 1962, Ser. No.163,689 1 Claim. (Cl. 74243) The invention described herein may bereadily understood in relation to use of the sprocket wheel inconnection with chain saws. In chain saws, a sprocket wheel is mountedupon a drive shaft and drives an endless chain carrying saw teeth. Inthe course of using chain saws, it is found that the sprocket wheel mustbe very carefully related to the chain saw itself in the sense that itis composed of metals which do not effect great wear upon the segmentsof the chain linkage. Rapid wear of the chain link leads to earlydiscarding of the chain of the sprocket wheel at great expense.Accordingly, usually the teeth of the sprocket wheel are of a softermetal than the chain segments and in consequence they are rapidly Wornby engagement with the chain saw, and it is necessary that the sprocketwheels be replaced at very frequent intervals. This in itself is costly,although not nearly as costly as the chain saws, and it is desirablethat means be provided to reduce the cost of the sprocket wheels since alarge number of them are used over the life of the piece of equipment.Prior to this invention, it is not believed that this problem has beensatisfactorily solved.

According to this invention, a sprocket wheel is provided of theconventional type which is adapted to accommodate wear-covers on thesurfaces of the teeth, thus, providing a new surface for engagement withthe chain segments whereby the wear which would otherwise be taken bythe sprocket wheel is taken by the wearcovers. When the coverings forthe teeth of the sprocket wheel have themselves become worn to a pointwhere the proper engagement is not being made with the chain segments,the wear-covers may be easily removed and simply replaced by a new set.

In one embodiment of the invention, hereinafter to be more fullydescribed, each tooth of the sprocket Wheel is provided with itsseparate wear-cover. Thus, in an eighttooth sprocket wheel, for example,eight wear-covers would be necessary. In another embodiment of theinvention, also hereinafter more fully described, a single unit is soshaped as to cover all of the teeth of the sprocket wheel. As will beunderstood, this latter embodiment is of one piece construction. Each ofthese embodiments will be described.

In connection with the first embodiment, a sprocket wheel of theconventional type is provided having each of the individual teethmodified to provide slots which extend generally inwardly of the baseline of the teeth, the slots being for the purpose of accommodatingco-operating flange portions on each of the wear-covers.

There is a plurality of slots between each of the teeth, namely twoslots extending generally oppositely, each of the slots accommodatingadjoining wear-covers. The slots, teeth, and wear-covers are so relatedthat when the covers are in place upon the teeth, they abut each otheradjacent the pre-formed flange portions of the wear-covers at or neartheir lower extremities. It has been found that by providing thewear-cover in this fashion, i.e., with the pre-forrned portions lockinginto the teeth and each wearcover firmly abutting wear-covers adjacentlypositioned, they are retained by the sprocket wheel firmly in theirproper position and in normal use of chain saws they cannot be dislodgedand thrown from the sprocket wheel. This is an important accomplishmentinasmuch as it is quite obviously dangerous to provide a tool, the partsof which cannot be relied upon to stay firmly positioned, dangerous inthat pieces thus thrown may do serious in- 3,113,3l5 Patented Jan. 21,19%4 juryifto the operator and also may damage the chain saw itse In thesecond form of the invention, the unitary wearcover, heretoforementioned generally, is pre-formed and of flexible material in orderthat it may be fitted around the entire sprocket wheel and initiallylocked into position thereon.

The initial locking of the unitary wear-cover is accomplished byproviding a pair of slots beneath two adjacent teeth of the sprocketWheel, the slots being formed and positioned similarly as the slots inthe first embodiment of the invention. As will be appreciated, in thisform of the invention, the teeth are not covered by individual piecesand therefore renewing of the surfaces is accomplished in a somewhatsimpler manner. However, in this instance, it is found to be desirableto provide additional means for locking the unitary wear-cover in placeupon the sprocket wheel and for this purpose, at least one, andpreferably a pair of special co-operating sprocket wheel cover-plates isprovided.

As will be understood, normally a sprocket wheel is positioned betweentwo generally similar oppositely positioned circular plates and theassembly is mounted upon the drive shaft of the saw motor. The piecesare provided with shaft bearing surfaces co-operating with the driveshaft so as to be positively driven thereby. The chain saw contacts thesprocket wheel teeth thus driving the chain saw, and the cover platesare of sufficiently larger diameter than the sprocket wheel to provide achannel within which the chain saw travels.

In the second form of the invention, one of the cover plates is providedwith lockpins which extend vertically relative to the flat surface ofthe cover plate, the lockpins being positioned on the plate so that whenthe sprocket Wheel is positioned adjacently with the unitary wear-coverthereon, they register with the area of the wear covers adjacent thebases of the sprocket wheel teeth. Thus, a plurality of the lockpins arestrategically positioned upon the cover plate so as to co-operate withthe sprocket wheel and provide relatively strong frictional engagement,thereby serving to prevent movement of the unitary cover from itsintended position. It will be understood that the sprocket wheel coverplate just referred to rotates with the sprocket wheel and that there isno possibility that the unitary cover can become dislodged from thesprocket wheel. Desirably, an outer cover plate having sockets thereinpositioned to receive the lockpins carried by the inner plate isprovided whereby to reduce any strain which may occur upon the lockpinsas the saw is operated.

This form of the invention has several advantages to recommend it. Itmay be readily stamped to a pre-formed configuration. Because of itsunitary construction, it may be manufactured cheaply. It affords anextremely rapid means of renewing the surfaces of the teeth and itpositively retains its position under all conditions of use.

It will be appreciated that the foregoing generally described forms ofthe invention provide substantial improvements over attempts which havebeen made heretofore to solve problems of the type generally incurred insprocket wheels which are utilized for driving metallic parts,particularly chain saws, and that it is an object of this invention toprovide such apparatus in the forms mentioned.

Before proceeding to describe the invention in more complete detailrelative to the drawings which are appended hereto, it is desired topoint out that the, wearcovers may be formed of any material which isknown to be suitable, e.g., stainless steel.

Referring now to the drawings,

FIGURE 1 is a view in front elevation of a sprocket wheel pre-formed andconstructed according to this invention, but without the wear-covers ofthis invention.

FIGURE 2 is a view in side elevation of the sprocket wheel illustratedin FIGURE 1, which view shows the details of the invention withparticular regard to the slots which are formed in the sprocket wheelbody.

FIGURE 3 is a view in front elevation showing the sprocket wheel ofFIGURE 1 having individual Wearcovers positioned thereon according tothe first embodiment of the invention.

FIGURE 4 is an isometric view of a single wear cover suitable for use asillustrated in FIGURE 3.

FIGURE 5 is a front view of a pro-formed wear-cover provided accordingto a second embodiment of t re invention in position about a second formof sprocket wheel.

F.GURE 6 is an isometric view of a pair of sprocket wheel cover platesprovided according to this invention, one showing the lockpins and theother co-operating sockets therefor.

FIGURE 7 is a view in front elevation partly in section showing theassembly of FIGURE 5 positioned relatively to the lockpins of the coverplate.

FlGURE 8 is a sectional view of FIGURE 7 on the line 8--S but showingalso both cover plates in position.

Referring to FIGURE 1 of the drawings, numeral denotes a sprocket wheelpro-formed according to this invention having a central rectangularbearing surface 22 which surface adapts it for cooperation withsimilarly shaped shaft. Numeral 24 denotes teeth of which there areeight as shown, although the number as will be appreciated is not to anyextent critical. Numeral 26 denotes slots extending inwardly of thewheel body and entirely through the thickness of the sprocket wheel toits opposite side. As will be observed, the slots are substantially atright angles to the surfaces from which they extend. It has been foundthat an angle of provides highly satisfactory locking engagement withthe turned down portions of the wear-covers which are to be described inthe following paragraphs. However, this function may be accomplished bydisposing the slots at a diiferent angle, e.g., any angle of from about45 and up to about or more provides good locking engagement between thewear-covers and the body of the sprocket wheel. Angles less than 45 tendto give too little purchase on the wheel body whereas angles approachingprovide locking surfaces which are quite thin and may break away fromthe wheel body. The angles referred to may be described as thosegenerated by a line moving clockwise having as the base line a line inthe plane of the sloping sides of the teeth and perpendicularly to theapex edge of the teeth.

The relationship of the slots 26 with respect to the body of thesprocket wheel may be more fully observed in FIGURE 2.

The wear-covers of the invention are shown in position upon the sprocketwheel in FIGURE 3.

Referring to FIGURE 4 of the drawings, numeral 28 denotes generally thewear covers formed according to this invention. As will be observed uponreference to FIGURE 4 each wear-cover is shaped to conform to thecontour of the teeth of the sprocket wheel and to cover the entiredriving surface of the teeth. Numeral 30 denotes flanged portions on thewear-covers which extend across the width of the covers and extend fromthe wearcover at an angle as heretofore described. As will beunderstood, the angle of the flange is pre-formed so that it is similarto the angle of the slot in the sprocket wheel.

The slots in the sprocket wheel may be for-med initially and supplied atthe time the chain saw itself is purchased, the wheel being providedwith teeth of appropriate size to function properly with the chain saw.In this case when the teeth have become worn sufficiently to requirereplacement, sprocket wheel may be removed and the teeth filed to auniform configuration so as properly to accommodate the wear-covers.Preferably, however, sprocket wheels are supplied with new equipmentwhich have the wear-covers of this invention in position thus providinga ready-formed sprocket wheel to receive additional wear covers withoutthe need for the filing operation as the wear covers require to bereplaced.

in use, when the wear covers have become worn, they are simply andeasily removed from their position by forcing them axially of thesprocket wheel along the slots until they completely emerge from thelocked position. Similarly, new wear covers are slid into position uponthe surface of each tooth and the sprocket wheel is then ready forreuse. It is desired to emphasize once again that the locking of thewear-covers into position in the manner taught herein is important andit is also important that the covers abut each other along their width,suitably at or near their base line where the flange is turned inwardly.The abutting relationship serves to prevent the pie-formed wear coversfrom deforming in the course of their use. Deformation, which mayotherwise occur, leads to looseness of the wear-covers and the dangerthat they may be thrown from the sprocket wheel.

Referring now to a further embodiment of this invention as generallydescribed hereinabove, and with particular reference to FIGURES 5-8 ofthe drawings, numeral 32 denotes a pie-formed unitary wear-cover adaptedto conform to the configuration of the teeth of a sprocket wheel. Aswill be seen, the unitary wear-cover may be described as composed of aplurality of wear-covers joined together at their bases so that it isonly necessary to fit the cover around the sprocket wheel and lock it inposition as will be described presently. In practice it is formed as onepiece. Numeral 34 denotes flange portions on the unitary structureadapting it for co-operation with a pre-formed suitably slotted sprocketWheel. As described generally previously, this form of the invention isco-operatively associated with specially designed cover plates which maybe observed in FIGURES 6 and 8 and which are denoted by numerals 36 and38 respectively. On the inside face plate, i.e., numeral 36 andextending horizontally therefrom is a plurality of locking pins whichpins are denoted by numeral 40.

As will be seen, the locking pins are generally triangular in shape forthe purpose of adapting their easy and effective engagement between theteeth of the sprocket wh el when the wear-cover is positioned thereon asshown in FIGURES 7 and 8 of the drawings. Obviously, as many lockpins asdesired may be provided on the cover plate and, preferably, as many areprovided as is required for each tooth of the sprocket wheel.

In cover plate 55, numeral 42 denotes sockets oriented for cooperationwith lockpins 40. Interlocking of the pins and sockets is found tostrengthen and rigidify the assembl although such is not considered tobe essential and, if desired, the pins may simply extend for the widthof the teeth.

With the unitary cover in place upon the sprocket wheel, the renewedsprocket wheel is plac d in position upon the shaft and forced firmlyagainst the cover plate 36. As will now be understood, the lockpins thenseat themselves in the grooves between the teeth of the sprocket wheeland cover plate 38 is positioned as in FIGURE 8, thus positivelypreventing all movement of the unitary cover with respect to thesprocket wheel.

This form of the invention as indicated previously hereprovides atrouble-free, danger-free assembly and possibly may be regarded as themost desirable embodiment of tire invention because of the ease andrapidity with which it may be applied. As will be apnreciatcd, a wornunitary cover is very easily removed by reversing the procedure ofassembly, the unitary cover coming off as one piece.

Additionally, the sprocket wheel needs grooving at only one point and,as a matter of fact, if desired, the illustrated grooving may be omittedif a locking pin is supplied instead; however, the groove constructionis preferred for reasons indicated at other points in thisspecification.

While the invention herein has been described with respect to particularembodiments, those skilled in the art will appreciate that variousmodifications within the scope of the invention may be derived from theteachings herein. Accordingly, this invention is not to be restrictedunduly and is to be understood to extend to all modifications which flowfrom the teachings herein.

This application is a continuation in part of my prior application,Serial No. 90,597, filed January 18, 1961, now abandoned.

What is claimed is:

A preformed sprocket wheel having a plurality of teeth thereon, a seriesof slots between each of said teeth, said slots being in the bases ofsaid teeth and extending inwardly thereof at an angle of at least about45 and 15 6 Wear covers for each of said teeth positioned upon thesurface of said teeth, and having extended flanged portions mating withsaid slots, said wear covers abutting each other substantially along aportion thereof adjacent said flanged portions.

References Cited in the file of this patent UNITED STATES PATENTS170,049 Brooks Nov. 16, 1875 905,756 Skinner Dec. 1, 1908 2,062,627Whitehead Dec. 1, 1936 2,179,967 Thompson Nov. 14, 1939 3,059,491 Hoffet a1. Oct. 23, 1962

